Electrodeposition of manganese and molybdenum mixed oxide thin films and their charge storage properties

Creators Nakayama Masaharu

Creators Tanaka Akihiro

Creators Sato Yoshimine

Creators Tonosaki Tsuyoshi

Creators Ogura Kotaro

Manganese and molybdenum mixed oxides in a thin film form were deposited anodically on a platinum substrate by cycling the electrode potential between 0 and +1.0 V vs Ag/AgCl in aqueous manganese(II) solutions containing molybdate anion (MoO_4^<2->). A possible mechanism for the film formation is as follows. First, electrooxidation of Mn^<2+> ions with H_2O yields Mn oxide and protons. Then, the protons being accumulated near the electrode surface react with MoO_4^<2-> to form polyoxomolybdate through a dehydrated condensation reaction (by protonation and dehydration). The condensed product coprecipitates with the Mn oxide. Cyclic voltammetry of the Mn/Mo oxide film-coated electrode in aqueous 0.5 M Na_2SO_4 solution exhibited a pseudocapacitive behavior with higher capacitance and better rate capability than that of the pure Mn oxide prepared similarly, most likely as a result of an increase in electrical conductivity of the film. Electrochemical quartz crystal microbalance and X-ray photoelectron spectroscopy clearly demonstrated that the observed pseudocapacitive behavior results from reversible extraction/insertion of hydrated protons to balance the charge upon oxidation/reduction of Mn^<3+>/Mn^<4+> in the film.

[ISSN]0743-7463

[NCID]AA10461730

info:doi/10.1021/la050114u

[isVersionOf] [URI]http://pubs.acs.org/journals/langd5/index.html